It might have something wrong with the muscle or bone. Next vet visit get it x-rayed.
I am not sure what you mean but animal which walk on their hind legs have straight legs and they are called bipedalanimals.
You scare it and also it makes it mean.
It means its a human dumbo. idiot
its been bothered
it has Poisson oak
I don't understand what you mean, if you could describe how the kitten walks, this might help to determine what is happening. Like, the kitten is dragging it's hind quarters, or is trying to balance on it's front paws, or is pulling with front paws and pushing and moving back paws but gets no traction. Something that describes with detail how the kitten is walking, also age, kind, other health conditions. Anything might be helpful.
It means that your kitten is cold. You can wrap it in a blanket and gently rub it softly to try to warm it up. Maybe wrap it in an electric blanket.
I could be wrong, but every time I hear this its usually in reference to a homosexual joke, like a man being as straight as a dogs hind legs. Their legs aren't straight so it's a joke.
newts have four legs just like most animals have
I asume you mean sheep rams and the answer is no. They are unable to buck or kick out because of the set up of their hind legs.
if you mean hop then its because their hind legs are so much larger and stronger than their front legs, it's pretty much the only way they can move!
It's because it's excited. My dog does that too. :)